The Second Hokage's two biggest feats are: the creation of the Summoning: Impure World Ressurection technique and his unrivaled Water mastery.
"Tobirama was primarily known for his mastery of Water Release. He could perform powerful water-style techniques in areas that lacked bodies of water by creating his own water out of thin air or producing it from his mouth, and perform some of the most complex water-style techniques, such as the Water Release: Water Dragon Bullet Technique, with a single hand seal. This amongst other reasons is why he is revered as the greatest known Water Release manipulator in the series."
He also had great sensory abilities. By just placing a single finger on the ground, he could detect the prescence and number of enemies from considerable distances. Not only that, Minato Namikaze said that he was highly skilled in Space/Time Ninjutsu.
Adding to his abilities, he was skilled in taijutsu:
"Tobirama was also shown to have great physical prowess and a considerable amount of skill in the area of taijutsu, as well as good teamwork with his elder brother, Hashirama Senju."
Another important feature that Tobirama has that, not only further sustains my point that the Senju clan is better than the Uchiha clan in every possible way except Genjutsu, is his legacy to the Narutoverse. As a Senju member, he did so much for Konoha:
-he established the Academy
-he founded the ANBU
-he founded the Konoha Military Police Force